Uniting of finely divided iron with other metals



Patented Mar. 12, I940 UNM'ED STATES UNITIN G F FINELY DIVIDED IRON;WITH OTHER METALS William. H. Smith, Detroit, Mich.; Kathryn L. Smithadministratrix of William H. Smith, de-

ceased Renewed July 22, 1939 N 0 Drawing. Application July 29, 1936,Serial No.

9 Claims.

This invention relates to the uniting of finely divided iron with othermetals. Heretofore, in the uniting of finely divided iron, such assponge iron, with other metals, it has been customary, as

set forth in my Patents No. 1,775,358 of Septemher 9, 1930, and No.1,951,499 of March 20, 1934, to mix the finely divided iron and otherelements together in a predetermined relationship before shaping, saidfinely divided other metals and 1% elements being either in theirnatural form or their oxide state.

It is the object of the present invention to obtain the combining andthe alloying or partial alloying by introducing. the alloying elementsfrom the outside of a mass of finely divided iron. It has beendiscovered that finely divided metallic iron or sponge iron of the typereduced from the ore without melting forms into a high crystalline stateabove 2000 F. and, of course, below its melting temperature ofapproximately 2800 F.

It is another object of the present invention to alloy or partiallyalloy the finely divided iron with non-ferrous metals at temperatureswillcient to produce fluidity of the non-ferrous metals so that thefluid non-ferrous metals will penetrate into and unite the finelydivided iron and alloy therewith at the grain boundaries of the iron.The non-ferrous metals penetrating into the mass of finely divided ironnot only forms a bond for uniting the iron particles but fills thoseportions which heretofore have been voids or contain metallic oxides,etc., with nonferrous metal.

Another important feature of the present in- 35 vention has to do withthe use of an acid slag, introduced into the mass of finely divided ironin some form, and the heating of this acid slag to a temperaturesufiicient to render the same fluid; the acid slag attacking andremoving the metallic oxides, the acid slag and the oxides being removed by sintering and/or pressing of the mass of finely divided iron,the removed oxides and slag being replaced by a non-ferrous metal.

In carrying out the invention I preferably use an iron which Iterm.sponge iron which is an iron produced by the separation of oxygenfrom iron ore without melting. In carrying out my preferred process thefinely divided metallic iron is first fabricated into any desired formby rolls or pressing and then sintering, or by placing in a mold andbonding, or any other well known fabrication process. The density ofthis mass of finely divided iron may, of course, vary con siderably butonce having been formed into the desired shape it is immersed in amolten bath of non-ferrous metal such as copper, nickel, aluminum, orany other combination containing non-ferrous metals.

The mass of finely divided iron may be heated above 2000 but less thanits melting temperature I before immersion, or it'may be brought to atemperature above 2000 by the immersion step, if the non-ferrous bath isabove said 2000 F., or operate at such lower temperatures as fiuidity ofthe non-ferrous bath permits to efiect its en- 1. tering the mass offinely divided iron.

It will be understood that the present process relates only to finelydivided iron not molten and that it also deals with any combination ofnonferrous metals and that the heat may be applied a to both the ironform and the non-ferrous metal simultaneously or separately; the gist ofthis step is that the molten non-ferrous metals enter the crystallinestructure of the iron form or mass from the outside.

It will be understood that the form of finely divided iron may bemechanically pressed or placed under temperature but that when it isbrought to the required temperature of above 2000 it will be in acrystalline sintered form. In 25 one form of carrying out the inventionthe iron form may be cylindrical in shape and then immersed in a bath ofnon-ferrous metal, the step being carried out in a reducing ornon-oxidizing atmosphere. The copper or nickel or other metal 80 willflow in and around through the crystals formed by the finely dividediron particles and alloying thereto, the alloying step taking placeparticularly at the grain boundaries of the iron.

By this process it will be seen that I am using the second non-ferrousmetal, whatever may be its form, to unite the crystals formed in thefinely divided iron mass at a predetermined temperature. The stepgreatly increases the ductility of the form and renders the samepractically rust- 40 less and very strong. In the case of thecylindrical form the interior thereof may be subjected to one kind ofnon-ferrous metal and the exterior to another kind of non-ferrous metalso that the same may be used as a bearing. When the article is removedfrom the bath the surplus may, of course, be drained off.

A preferred method of treating the finely divided iron form and ofgetting a non-ferrous metal into the form, where the finely divided ironcontains metallic oxides, and particularly iron oxides, is to subjectsuch oxides to a fluid acid slag. The acid slag in its natural state maybe mixed with the finely divided iron or may be introduced from theoutside in a molten state, or the finely divided iron form may beimmersed in a bath containing a molten non-ferrous metal and an acidslag. Whatever the form in which the acid slag is introduced into theiron form, such acid slag will remove the basic oxide formed in thevoids and grain boundaries of the iron form and replace the same with amolten non-ferrous metal. When the finely divided iron form is subjectedto the sintering temperature it materially contracts to a lesser volumeand in doing so forces or squeezes out the slag and oxides; if the formis subjected to pressure as well as temperature, this application ofpressure will serve to assist in squeezing out slag and oxides, thenon-ferrous metals having a greater surface tension will remain in thevoids and grain boundaries. Thus it will be seen that I may introducethe alloying non-ferrous metals into the form regardless of whether thevoids and grain boundaries in said form are entirely open and free orwhether they are filled with an oxide.

The acid slag, which may be utilized to remove the basic iron oxide orthe like, may be borax, acid silicates, or any well known acid slag.(Typical acid silicates are It will be understood here that the ironoxide may be present in the sponge iron when reduced or the iron formmay be subjected to an oxidizing temperature; in. either case, the stepof removing the iron oxide or the like, may take place in a reducing oroxidizing atmosphere, as the acid effect overcomes any atmospherecondition.

As a general rule, silica will be present in the reduced sponge ironalong with a small amount of iron oxide occasioned by its completereduction. The silica is. acid and has a high melting point, but byadding sodium carbonate to the briquet the resulting compound has amaterially reduced melting point; I prefer to add a relatively smallamount of sodium carbonate as compared to the silica and, while thesodium carbonate is basic, when compounded with the silica, theresulting compound remains predominately acid. The compound of silicaand sodium carbonate produces an extremely fluid acid slag and this willtackle the iron oxide and remove the oxide from the metallic iron of theform. Thus, by adding the sodium carbonate to the silica I materiallyreduce the melting point, obtain a very fluid acid slag which cleans thesponge iron form and takes out the iron oxide. In place of sodiumcarbonate I may use potash, sodium chloride, or similar compounds whichwill reduce the melting point and increase the fluidity of the silica.as an acid slag.

Whether the acid slag used in removing the oxide is formed by the addingof powdered sodium carbonate or the like to the silica already in theform, or by adding boric acid or the like or by combining the moltenslag with molten nonferrous metal bath, the slag used is preferably onethat becomes relatively fluid at some point below the melting point ofiron. The melting of the slag is an exothermic action, and creates heat,and if an acid slag were used that melted, say, at 2000 and the briquetis sintered at 2000, then the treatment would take a very few minutes;it is a question of time and temperature, and in some cases where thetemperature would not be sufilcient to produce the exothermic action andthe slag melted very slowly, as long as half an hour would be requiredfor the treatment. The

fluid acid slag cleans the lattice-work and the grain boundaries byfreeing the iron oxide or the like from the iron with which it wasassociated or combined.

The acid slag treatment has a beneficial action regardless of theintroduction of non-ferrous metals into the form; if molten non-ferrousmetals are not introduced into the interstices and the grain boundariesof the form, a small amount of acid slag will remain and give abeneficial rust protection when the form is finally pressed or rolled toshape.

Even if the forms of finely divided iron were to be subjected to amelting temperature, it would still be possible to slag out the oxidesbefore reaching the melting point of the iron, so that the oxides arenot carried into the molten bath.

By predetermining the'composition of the sla in the finely divided ironbriquets or forms, so that slagging takes place before the iron becomesmolten, it is possible to utilize the phenomena of metallic contractionproduced by the sintering of finely divided iron to squeeze out the slagand associated oxides to clean the iron form. It will also be obviousthat pressure applied during or just after the sintering step willmaterially assist in the squeezing out of slag and oxides. The finalforms in my process may be subjected to further working such as throughrolls, extrusion, or to any kind of working whatsoever, although it willbe distinctly understood that such forms are commercially usableimmediately after the alloying or partial alloying step.

In another modified process I may use a vitreous enamel powder which maybe placed on the outside of the form or for that matter may be mixedwith a considerable portion of the cross sectional area of the finelydivided iron mass or form. The form may be shaped or worked as desiredinto sheets or into the final article and when the form is subjected tothe fusing temperature, as is customary in enameling articles, theenamel will be permanently locked within the finely divided ironadjacent the surface of the article thus eliminating all flaking andmaking permanent union of porcelain and iron in composite mass.

What I claim is:

1. The process of forming iron which consists in subjecting a mass ofsintered finely divided iron having iron oxide in the voids and grainboundaries thereof to a bath of acid slag containing molten non-ferrousmetals of such fluidity as to enter the interstices of the mass,removing the oxide in the mass of finely divided iron by said slag andreplacing the same with non-ferrous metal.

2. The process of forming iron which consists in subjecting a mass offinely divided iron having been sintered and having iron oxide in thevoids and grain boundaries to a bath of molten acid slag, therebyremoving the iron oxide in the mass of finely divided iron by said slagand then replacing such slag with molten non-ferrous metals.

3. The process of forming composite metallic articles which consists informing finely divided iron particles into any desired shape, a portionof said shape containing iron oxide, sintering and predeterrnining theporosity and crystalline structure of said shape by preheating and thensubjecting said shape to an acid slag whereby said fluid slag enters thevoids and interstices of said shape.

4. The process of forming substantially rust proof composite metallicarticles which consists in forming finely divided iron particles intoany desired shape, predetermining the porosity and crystalline structureof said shape by preheating and sintering, the iron and similar oxidesconcentrating at the grain boundaries formed by sintering, subjectingsaid sintered shape to a bath of acid slag of such a nature and fluidityas to enter the voids and grain boundaries and react with and remove thebasic oxides at such grain boundaries.

5. The process of forming substantially rust proof composite metallicarticles which consists in forming finely divided iron particles intoany desired shape, predetermining the porosity and crystalline structureof said shape by preheating and sintering, the iron and similar oxidescon centrating at the grain boundaries formed by sintering, subjectingsaid sintered shape to a bath of acid slag of such a nature and fluidityas to enter the voids and grain boundaries and remove the basic oxidesat such grain boundaries, and replacing the oxides removed from saidgrain boundaries with a molten non-ferrous metal.

6. The process of forming iron which consists in subjecting a mass offinely divided iron having metallic oxides in the voids and grainboundaries thereof to fluid acid slag and fluid nonferrous metal of suchfluidity as to enter the interstices of the mass, subjecting the mass offine- 1y divided iron to a sintering temperature sufficlent to contractthe finely divided metals and squeeze out the slag and oxide butretaining at least a portion of the non-ferrous metals.

7. The process of forming iron which consists in forming a mass offinely divided iron having iron oxide in the voids and grain boundariesthereof, introducing an acid slag into the said mass of the type thatwill have sufiicient fluidity as to enter the interstices of the masswhen subjected to a temperature less than the melting point of the iron,subjecting the mass of finely divided iron and slag to a sinteringtemperature sufilcient to predetermine the porosity and-crystallinestructure of the mass, the sintering temperature being sumcient to meltthe acid slag whereby the same attacks the basic iron oxide andsuflicient to contract the mass to squeeze at least a portion of thefluid slag and iron oxide therefrom.

8. The process of forming iron which consists in forming a mass offinely divided iron having iron oxide in the voids and grain boundariesthereof, introducing an acid slag into the said mass of the type thatwill have sufiicient fluidity as to enter the interstices of the masswhen subjected to a temperature less than the melting point of the iron,subjecting the mass of finely divided iron and slag to a sinteringtemperature sufiicient to predetermine the porosity and crystallinestructure of the mass, the sintering temperature being sufiicient tomelt the acid slag whereby the same attacks the'basic iron oxide andsufiicient to contract the mass to squeeze at least a portion of thefluid slag and iron oxide therefrom, and subjecting said mass of finelydivided iron to pressure to assist in squeezing out the fluid slag andoxide.

9. The method of treating finely divided iron reduced without melting,of the type having a small amount of silica and other oxides, whichcomprises mixing a quantity of sodium carbonate with the mass andcompressing the same into a predetermined shape, heating the mass to asintering temperature under the melting point of iron but sufiicient toform iron crystals, whereby the iron and similar oxides are concentratedat the grain boundaries formed by the sintering step, the quantity ofsodium carbonate being suificient relative to the silica that when themass is further sintered, but still under the melting point of the iron,the molten sodium carbonate will combine with the silica to form aresulting silicate which remains acid in its efiect and continuing thesintering of the form at a temperature sufficient to contract the massand utilizing the metallic contraction of the finely divided metals tosqueeze out at least a portion of the silicate and associated oxides.

WILLIAM H. SMITH.

